Thermostat



Aug. 18, 1953 H. A. MULVANY ETAL.

THERMOSTAT 2 Sheets-Sheet 1 Filed Feb. 26, 1951 INVENTOR5.

Harry A. Mulvany BY Richard B.Mulvany W/WZM Aug. 18, 1953 H. A. MULVANY ETAL 2,649,523

THERMOSTAT Filed Feb. 26, 1951 2 Shee ts-Sheet 2 INVENTORS. Harry A.Mulvany Richard BMulvany Patented Aug. 18, 1953 2,649,523 OFFICE THERMOSTAT Harry A. Mulvany and Richard B. Mulvany, Berkeley, Calif.

Application February 26, 1951, Serial No. 212,764

11 Claims. 1

This invention relates to a thermostat of the bimetallic type in which the expanding or actuating element will be of comparatively large area and so positioned that it will be exceptionally sensitive and responsive to temperature variations in a room or space which is to be maintained at a substantially constant temperature.

The object of the invention is generally to improve and simplify the construction and operation of thermostats; to provide a thermostat of the bi-metallic type in which the expanding element is of such large area and so positioned and exposed that it will be exceptionally sensitive and responsive to temperature variations; to provide a thermostat which is composed of a single expandable member, to which is secured a pair of substantially nonexpanding members, said members being flexible and bowed in opposition to each other to permit doubling or compounding of the movement of the expanding member, and in conjunction therewith to provide a lever which is actuated by the compounded movement of the flexible members; to provide an electric circuit making and breaking mechanism which is actuated by the lever; and further, to provide a calibrated temperature controlling and indicating drum, and an adjustable mounting therefore whereby the spacing between the contacts of the circuit making and breaking mechanism may be readily adjusted.

The thermostat is shown by way of illustration in the accompanying drawings in which:

Fig. l is a perspective view of the wall plate of the thermostat said view showing the rear side of the plate and the mechanism carried thereby.

Fig. 2 is a perspective view of the back plate.

Fig. 3 is an enlarged vertical section of the adjustable stationary contact I of the circuit making and breaking mechanism.

Fig. 4 is a vertical central longitudinal section of the temperature indicating drum together with its stem and adjusting nut.

Fig. 5 is a vertical cross section of a wall structure showing an outlet box and the thermostat installed therein, said view being partially in section and broken away to show an end view of the mechanism of the thermostat; and

Fig. 6 is a perspective view of the outlet box and the thermostat in position to be installed therein.

Referring to the drawings in detail and particularly Figs. 1-5 and 6A indicates an elongated rectangular shaped plate constructed of aluminum or a similar material having a high coefficient of expansion. Formed at opposite ends of the plate and on the rear side thereof are pairs of pads 22 and 33 and extending lengthwise of the plate and secured to the pads are strips 4 and 5 constructed of a metal having a low coefficient of expansion and known to the trade as Invar. The Invar strips are flexible and are bowed in opposition to each other, hence, when the plate or the expandable member lengthens due to a temperature rise the bow in the respective strips flattens and conversely increases with a temperature drop. This change in the bowing of the strips compounds the expanding or contracting movement of the plate and is utilized to operate a lever 6 which in turn actuates an electric circuit making and breaking mechanism hereinafter to be described.

Secured to the strip l substantially midway between its ends is a yoke shaped member 1 which forms a pivotal support for one end of the lever 5, and secured to strip 5 is a nut 8 and a cooperating screw 9 which carries a drum it and a stem ll, said stem engaging the under surface of the lever ii at a point sli htly forward of its pivot. Stem l I forms a fulcrum point for lever 5 thereby materially multiplying or increasing the movement of the free end 6* of the lever, i. e., when-the plate A expands or lengthens due to temperature rise the strips 4 and 5 tend to flatten or move toward each other, thus the yoke l to which the lever is attached moves in the direction of arrow a while nut 8 and stem ll moves in the direction of arrow I) this causes the short end of the lever which is on the left hand side of the fulcrum to move down and the long free end of the lever on the right hand side of the fulcrum to move upwardly. This distance the free end moves will of course depend on the expanding movement of the plate, this movement is compounded or doubled by the bowed strip and finally multiplied by the lever. In actual practice with a plate eight inches long and a lever ratio of twenty to one a movement of approximately one-sixteenth of an inch at the free end of the lever is obtained with a temperature change of one degree Fahrenheit.

The electric circuit making and breaking mechanism comprises a pair of contacts indicated at l2 and I 4, the contact I2 being secured to a laterally extending arm l2 which is secured to the free end 6 of the lever. The contact I4 is secured in and carried by a back plate best shown at B in Figs. 2 and 5. The back plate is formed of a plastic insulating material and so is the laterally extending arm [2 The back plate carries a contact I4 and a terminal member 15, it also carries three bosses indicated at 2 -3 and I6 which bosses register with bosses li -3 and Ili formed on the rear side of plate A. The bosses serve as spacers and supports between the plates A and B and screws extending through the bosses secures plate B to plate A. When the plates are assembled as shown in Fig. 5 contact It will align with and assume a position directly below contact I2 and inasmuch as contact [2 is carried by the lever 6 it will move to or away from contact I 4 when the thermostat is in operation.

The electric circuit to be controlled by the thermostat is carried by the wires indicated at closed and conversely broken when the contacts separate.

The drum ll] together with its adjustable support, to wit, nut 8 and screw 9 serves several important functions. First, the drum is calibrated and numbered to indicate the temperature to .loe;

maintained, a portion .of the drum extends through a slot formed in plate A as is clearly shownin Figs. 5 and6 and thus displays the calibrations, for instance, if the numeral! lines up with the arrow 2c in Fig. '6 that will be the temperature at which the contacts of the circuit making and breaking, mechanism will separate if the temperature in the room or space to be controlled rises above m'degrees. Second, the drum assembly forms a fulcrum point for lever 6. Third, by applying finger pressure to the face of the drum it may be rotated to change the temperature setting, either to raise orv lower thetemperature as rotation of the drum raisesor lowers the free end of the lever B and thereby increases or decreases the spacing between the circuit making and breaking contacts. Fourth,-when adjusting the thermostat in the factory, for instance, in a room where .the temperature is maintained at '70 degrees Fahrenheit, it may happen that when the contacts are in the correct position the '70 degree reading on the .drum is not visible through the slot .or not quite in register with the arrow 20. ,If'. that is the case, a nut 8 which secures nut 8 to strip 5 (see Fig. 4) is loosened, thereby making it possible to turn nut. ll screw 9 and drum H] as .a unit until the '70 degree reading on the drum registers with arrow 26 after which the nut 8 is tightened and a correct setting of the drum is made without disturbing the spacing between the contacts.- It may happen that after drum adjustment has been corrected, that the spacing between the contacts should be slightly adjusted, this .isreadily accomplished as contact I4 is adjustable as shown in Fig. 3.

In actual practice the thermostat is. designed for installation in. astandard form of outletbox such as indicated .atC, see Figs. 5 and 6. Such boxes are usually provided withflugs 24 so that the box may be nailed and rigidly secured to the studding' 25 of a wall structure. The .open side of the box projects outwardly from the face of the studdinga distance equal to the thickness -of the plaster 25 or other wall surfacing material employed so as to be flush with the surface when the wall is. finished, thus when the thermostat is to be installed all the electrician has to .do is to connect the wires l'l'and H? to their respective terminals, then insert the thermostat. in the. box and finally secure it in place by screws 21 which pass throughthe respective ends of the wall plate and enter threaded lugs 28 formed at each end of the outlet box. With the thermostat installed the only element that vwill be exposed in the room or space where ,thetemperature is to becontrolled is the wall plate. The plate is flushwith the wall surface and is so large in area as to be instantly affected bytemperaturechanges.

The wall .plateserves several important functions, first, it servesas vacover or wall plate for the outlet box,. secondly, the -plate shields and protects all of the ,mechanism of the thermostat, third, it serves as a support and mounting forall of. the mechanism of. the. thermostat, and: fourth,

by. utilizing the platerA as: a .wall..-p1ate .1ancl.:.c.on-

structing the plate ofa metal having. a high coefficient of expansion, an expandable member of large area is provided and as the entire outer surface of the expandable member is exposed to the room or space to be heated it is obvious that it .will be exceptionally sensitive and responsive to temperature variations, the plate will accordingly expand or contract substantially in unison -with-temperatu-re changes, and as the plate is the main or only actuating element of the thermostat a substantially uniform temperature will be maintained in the room or space in which the thermostat is placed. The temperature to be maintained may be changed at any time by rotating the drum in either direction to change the temperature setting; the drum remaining where set as it is frictionally held by a spring actuated friction shoe 30. The, drum may only be rotated one revolution as a stop lug 3! on the drum engages a similar lug 32 on the wall plate.

While certain features of our invention have been more or less sepcifically described and illustrated we wish it understood that changes may be resorted to within the scope of the appended claims, and that the specific materials and finish of the parts employed may be such as the manufacture may dictate or varying uses may demand.

Having thus described and illustrated our invention, what we claim and desire to secure by Letters Patent is:

1. In a thermostat for controling and inaintaining a substantially constant room temperature, a wall plate adapted to form a cover for an electric outlet box, said wall plate being made of a material having a high coefficient of expansion and presenting an area so large as to be exceptionally sensitive and responsive to ternperature variations, a pair of spaced apart flexible members extending lengthwise of the wall plate and anchored at their opposite ends thereto said members being bowed in opposition to each other and being made of a material having a low coeflicient of expansion, an. electric circuit making and breaking mechanism, and means actuated by the wall plate and the bowed members for operating the electric circuit making and breaking mechanism.

,2. In a thermostat for controlling. and maintaining a substantially constant room temperature, a wall plate adapted to form a cover for an electric outlet box, said wall plate being made of a material having a high coeflicient of expansion and presenting an area'so large as to be exceptionally sensitive. and responsive to temperature variations, a pair of spaced apart flexible. members extending lengthwise of the wall plate and anchored at their opposite ends thereto said members being bowed-in opposition to each other and being made of a material having a low coefficient of expansion, a lever pivoted at one end to one of the flexible members the other end of the lever being free, a member secured to the other flexible strip said member engaging the lever at a :point adjacent its pivot and forming a fulcrum therefore, a stationary contact member, a second contact member carried by the free end of the lever and movable to and away from the stationary contact to make or break an electric circuit.

3. In a thermostat for controlling and 'maintaining .a substantially constant room temperature, a wall plate adapted to form a cover for an electric outlet box, said wallplatebeing :made of'a material having ahigh coefflcient. of expansicn and presenting an area so large as to be exceptionally sensitive and responsive to temperature variations, a pair of spaced apart flexible members extending lengthwise of the wall plate and anchored at their opposite ends thereto said members being bowed in opposition to each other and being made of a material having a low coefficient of expansion, a lever pivoted at one end to one of the flexible members the other end of the lever being free, a member secured to the other flexible strip said member engaging the lever at a point adjacent its pivot and forming a fulcrum therefore, a stationary contact member, a second contact member carried by the free end of the lever and movable to and away from the stationary contact to make or break an electric circuit, and means for increasing or decreasing the length of the fulcrum member to increase or decrease the spacing between the contacts.

4. In a thermostat of the character described the combination with the wall plate, the pair of bowed strips extending lengthwise thereof and anchored thereto and the lever pivoted at one end to one of the bowed strips, of a fulcrum member for the lever, said member comprising a nut carried by the other bowed strip, a screw extending from the nut and engaging the lever at a point adjacent its pivot, and means for rotating the screw with relation to the nut to lengthen or shorten the fulcrum member.

5. In a thermostat of the character described a wall plate, a pair of bowed strips extending lengthwise thereof and anchored thereto, a lever pivoted at one end to one of the bowed strips the opposite end of the lever being free, a fulcrum member for the lever said member comprising a nut carried by the other bowed strip, a screw extending from the nut and engaging the lever at a point adjacent its pivot, means for rotating the screw with relation to the nut to lengthen or shorten the fulcrum member, and means for frictionally resistin rotation of the screw.

6. In a thermostat of the character described, a wall plate, a pair of bowed strips extending lengthwise thereof and anchored thereto, a lever pivoted at one end to one of the bowed strips, a fulcrum member for the lever, said member comprising a nut carried by the other bowed strip, a screw extending from the nut and engaging the lever at a point adjacent its pivot, means for rotating the screw with relation to the nut to lengthen or shorten the fulcrum member, and means for rotating the screw and nut in unison without changing the length of the fulcrum member.

7. In a thermostat of the character described a wall plate, a pairlof bowed strips extending lengthwise thereof and anchored thereto, a lever pivoted at one end to one of the bowed strips, a fulcrum member for the lever, said member comprising a nut carried by the other bowed strip, a screw extending from the nut and engaging the lever at a point adjacent its pivot, means for rotating the screw with relation to the nut to lengthen or shorten the fulcrum member, means for rotating the screw and nut in unison without changing the length of the fulcrum member. means for securing the nut a ainst rotation, and means for frictionally resisting rotation of the screw.

8. In a thermostat of the character described a wall plate, a pair of bowed strips extending lengthwise thereof and anchored thereto, a lever pivoted at one end to one of the bowed strips the other end of the lever being free, a station-' ary contact member, a second contact member carried by the free end of the lever and movable to or away from the stationary contact to make or break an electric circuit, a nut carried by the other bowed strip, a screw extending from the nut and engaging the lever at a point adjacent its pivoted end and forming a fulcrum point for the lever, a drum secured to the screw to rotate the screw in the nut and thereby raise or lower the fulcrum point with simultaneous increase or decrease in the spacing between the contacts, and means for frictionally resisting rotation of the drum and screw.

9. In a thermostat of the character described a wall plate, a pair of bowed strips extending lengthwise thereof and anchored thereto, a lever pivoted at one end to one of the bowed strips the other end of the lever being free, a stationary contact member, a second contact member carried by the free end of the lever and movable to or away from the stationary contact to make or break an electric circuit, a nut carried by the other bowed strip, a screw extending from the nut and engaging the lever at a point adjacent its pivoted end and forming a fulcrum point for the lever, a drum secured to the screw to rotate the screw in the nut and thereby raise or lower the fulcrum point with simultaneous increase or decrease in the spacing between the contacts, means for frictionally resisting rotation of the drum and screw, means for rotating the nut, the screw and the drum in unison without changing the spacing between the contacts, and means for securing the nut against rotation.

10. In a thermostat for controlling and maintaining a substantially constant room temperature, a wall plate adapted to form a cover for a box, said wall plate being made of a material having a high coefiicient of expansion and presenting an area so large as to be exceptionally sensitive and responsive to temperature variations, a fulcrum member, a lever supported thereby and means for imparting expansion or contraction movement of the plate to the short end of the lever.

11. In a thermostat for controlling and maintaining a substantially constant room temperature,. a wall plate adapted to form a cover for a box, said wall plate being made of a material having a high coefficient of expansion and presenting an area so large as to be exceptionally sensitive and responsive to temperature variations, a fulcrum member, a lever supported thereby, means for imparting expansion or contraction movement of the plate to the short end of the lever, and means for raising or lowering the fulcrum member.

HARRY A. MULVANY. RICHARD B. MULVANY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,042,244 Macklin Oct. 22, 1912 1,166,081 Royall Dec. 28, 1915 2,496,917 Poitras Feb. 7, 1950 FOREIGN PATENTS Number Country Date 339,200 Great Britain Dec. 11, 1930 

